Stabilization of chlorinated hydrocarbons with nitriles



United States Patent Ofitice s 029 29s STABILIZATION F crrLomNA'nsnHYDRO- cAnBoNs WITH NITRILES Fred S. Hirsekorn and John H. Rains,Wichita, Kans,

3,029,298 Patented Apr. 10, 19:32

water is added. Strips of electrolytic copper 2.0 x 7.5 x 0.005 cm. arethoroughly cleaned and weighed. One strip is inserted in the flask so asto be substantially completely immersed in the liquid. A Soxhlctextractor havassignors to Frontier Chemical Company, Division of 5 ing avolume of approximately 70 m1. is attached to the z g o lfl g p y,Wifihita, K2115 3 1 flask and a second copper strip is inserted into theextracon ew i tor. A small Allihn condenser is mounted on top of the Nog' l E} 20542 Soxhlet extractor and a third copper strip is placed inthe aims condenser so that the perchlorethylene condenses on the Thisinvention relates to the stabilization of halogenated strip. A 100 wattfrosted Mazda incandescent light bulb aliphatic hydrocarbons such asperchlorethylene and to the is placed one inch from the extractor vaportube to supply stabilized composition, the stabilizer being selectedfrom energy for photochemical oxidation. The flask is heated the groupconsisting of 3-'butenenitrile, methacrylonitrile, by suitable means soas to reflux the composition at a and mixtures thereof. rate whichcauses the extractor to empty about once every It is known thatchlorinated hydrocarbons such as eight to-ten minutes. These conditionsare maintained perchlorethylcne have a tendency to decompose during forthe duration of the test which is usually 24 hours but storage, shipmentand sometimes use. This tendency be may be longer. The condenser isattached to a water comes more pronounced when the chlorinatedhydroscrubber to absorb any hydrogen chloride which may be carbon is incontact with metals such as copper, steel, evolved during the test.aluminum, brass, etc., and/or is exposed to heat, moisture 0 After thetest is complete the flask is cooled and a and light. Such decompositionresults in the formation quantity of water equal to the perchlorethylenesample of hydrogen chloride and phosgene, among other objecis pouredthrough the condenser and extractor into the tionable decompositionproducts. These may cause seriflask to absorb any acid. The contents ofthe flask are ous corrosion of metal in dry cleaning machines and shakenand the acidity developed during the test is determetal degreasingunits. The acidic products of decom- 25 mined by sodium hydroxidetitration using bromothymol position may be detrimental to fabrics andto many dyes. blue as the indicator. Consequently, materials which willinhibit or prevent the The loss in weight in milligrams of the copperstrips decomposition of these chlorinated hydrocarbons are suspended inthe flask, extractor and condenser are deterusually added. mined andtotaled. According to paragraph 14 of the In abroad embodiment thepresent invention comprises N.I.D. specification 3-5 5 a maximum loss of90 mg. adding to a chlorinated hydrocarbon such as perchlor- (0.001grams per square centimeter exposed) is permisethylene, a small buteffective amount of a stabilizer comsible. As a practical matter forsatisfactory commercial prising S-butenenitrile, methacrylonitrile, andmixtures stabilization of the dry cleaning solvents such asperchlorthereof. The stabilizers may be added in proportions ethylene,the loss should be less than about 10 mg. over from about 0.005% toabout 1.0% by Weight of the a 24 hour exposure period for satisfactorystabilizer perchlorinated hydrocarbon although as a rule the stabilizersformance. are not required in amounts exceeding about 0.2% to In view ofthe fact that the perchlorethylene or other 0.5%. solvent is recoveredby distilling it so as to separate the Perchlorethylene is thechlorinated hydrocarbon with materials extracted during the dry cleaningoperation, the which the invention is most particularly concernedalstabilizer should boil in a range such that it will pass though it isalso applicable to other chlorinated hydrooverhead with the solventduring the distillation. It carbons such as chloroform, methylenechloride, dichlorshould leave no spots or stains on fabrics after thesolethylene, trichlorethylene and the like. vent has been completelyevaporated following completion The chlorinated hydrocarbons containingfrom one to of the dry cleaning cycle. The color of the stabilizedsolfour carbon atoms are Widely used as solvents in industry. vent mustremain Water white after stabilization and after The lower boilingliquid chlorinated hydrocarbons such as the recovery step. The residueafter solvent evaporation perchlorethylene are widely used in the drycleaning inmust be below about 0.016 gram per 100 ml. of solvent. dustrywhere the problem of decomposition of the sol- Preferably the stabilizershould be stable and should vent may become acute due to corrosion ofequipment stabilize the chlorinated hydrocarbons against decomposiandadverse eifect upon the garments cleaned. In the tion both in darkstorage and when exposed to light. examples which are set forth hereinthe efiectiveness of In Table I are shown the results of tests using theabove the stabilizer was determined according to Method N.I.D. describedmethod in which perchlorethylene only was used Specification 3-55 of theNational Institute of Dry Clean and perchlorethylene was tested usingfrom about 0.005 to ers. Briefly, this method consists of refluxingperchlorapproximately 0.1% of methacrylonitrile. The test periodethylene or other halogenated hydrocarbon under test in was twenty-fourhours with the exception of one test a flask in the presence of waterand strips of copper. One which was carried out for a period of 72hours. In one hundred ml. of the stabilized perchlorethylene is measuredtest the perchlorethylene also contained about 1.0% of a into a 300 ml.round bottom flask and 0.2 m1. of distilled commercial detergent whichwas Vividol-LT.

TABLE I Weight Dura pH Weight Loss-Milligrams Percent tion of Acidity,Methacrylo- Test, ppm.

nitrile Hours Before After Flask Extractor Condenser Total 5.9 6.1 207.3219.3 as 8.2 27.2 38.2 0.6 0.7 1.3 2.6 0.4 1.5 1.2 3.1 0.3 0.7 1.6 as0.5 4.3 1.9 6.7 0.5 1.0 1.7 3.2 1.5 1.1 1.7 4.3 0.6 1.0 1.8 3.4

1 Copper strip badly corroded. 2 1% detergent.

The data in Table I establish that methacrylonitrile is efiective inreducing the copper corrosion according to the standard N.I.D. test inproportions of 0.005 to approximately 0.1%. Larger amounts of thestabilizer could be used but normally it is not required.

In concentrations of above about 0.01% the weight loss of the copperstrips was reduced well below 10 mg. and in fact was well below 5 mg.for the 24 hour test and only slightly above that for the 72 hour testperiod.

Methacrylonitrile also stabilizes other halogenated hydrocarbo-ns.Freshly prepared chloroform was stored for a two-week period in oneliter clear glass bottles with and without a clean steel coupon and withand without methacrylonitrile in proportions of 200 ppm. The averages ofacidity measured as HCl were as follows: With no stabilizer and withoutthe steel coupon acidity averaged 0.125%, and with thestabilizer=0.0l4%. in the presence of a steel coupon the control sampleaveraged 0.144% and the methacrylonitrile stabilized sample averaged0.061%. Two samples of each were stored. This shows that decompositionof chloroform was increased by the presence of the steel coupon but thatthe amount of decomposition was substantially reduced in the presence ofmethacrylonitrile.

In Table II are shown the results of a series of tests using3-butenenitrile in proportions from approximately 0.005% to about 0.1%over a 24 hour test period using the N.I.D. procedure described above.In one instance 1.0% of the commercial detergent Vividol-LT was used.

TABLE II fl-Butenenitrile The results show that in proportions aboveabout 0.005% the 3-butenenitrile prevented the formation of acidity andreduced the loss of weight of the copper strip to well below mg.

3-butenenitrile likewise has been found to inhibit decomposition ofchloroform both in the presence and in the absence of a steel coupon.The control samples with and without the steel coupon are given above,with 3-butenenitrile in the proportion of 200 p.p.m. by weight of thechloroform averaged 0.005 1% without the coupon and 0.051% in the samplecontaining the steel coupon.

Ordinarily the stabilizer is added at the point of manufacture andpackaging of the perchlorethylene. It is added before any substantialdecomposition takes place. The finished composition is usually shippedto its destination in bulk, for example, in -gallon drums, in tank cars,or in trucks, although frequently smaller containers may be used. Thestabilizers of this invention do not impart objectionable odor or colorto the stabilized composition.

We claim as our invention:

1. A stabilized low-boiling chlorinated hydrocarbon selected from thegroup consisting of perchlorethylene and chloroform containing a smallbut effective amount of a stabilizer selected from the group consistingof 3-butenenitrile and methaorylonitrile and mixtures thereof, theproportions of said stabilizers being about 0.005% to about 1.0%.

2. Stabilized perchlorethylene containing about 0.005% to about 1.0% ofa stabilizer selected from the group consisting of 3-butenenitrile andmethacrylonitrile and mixtures thereof.

3. A method for stabilizing halogenated hydrocarbon selected from thegroup consisting of perchlorethylene and chloroform from decompositionunder conditions of storage and use which comprises adding thereto asmall but effective amount of a stabilizer selected from the groupconsisting of 3-butenenitrile and methacrylonitrile and mixturesthereof, the proportions of said stabilizers being about 0.005 to about1.0%.

4. A method for stabilizing perchlorethylene from decomposition underconditions of storage and use which comprises adding thereto about0.005% to about 1.0% of a stabilizer selected from the group consistingof 3- butenenitrile and methacrylonitrile, and mixtures thereof.

5. A method for stabilizing chloroform from decomposition underconditions of storage and use which comprises adding thereto about0.005% to about 1.0% by weight of a stabilizer selected from the groupconsisting of 3-butenenitrile and methacrylonitrile, and mixturesthereof.

6. Stabilized chloroform containing about 0.005% to about 1.0% by weightof a stabilizer selected from the group consisting of B-butenenitrileand methacrylonitrile, and mixtures thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,043,257 Missbach June 9, 1936 2,422,556 Klabunde June 17, 1947

1. A STABILIZED LOW-BOILING CHLORINATED HYDROCARBON SELECTED FROM THEGROUP CONSISTING OF PERCHLORETHYLENE AND CHLOROFORM CONTAINING A SMALLBUT EFFECTIVE AMOUNT OF A STABILIZER SELECTED FROM THE GROUP CONSISTINGOF 3-BUTENENITRILE AND METHACRYLONITRILE AND MIXTURES THEREOF, THEPROPORTIONS OF SAID STABILIZERS BEING ABOUT 0.005% TO ABOUT 1.0%.